1. Field of the Invention
The present invention relates to a developing apparatus for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device and, more particularly, to a developing apparatus capable of forming a high-definition image using a single component system developer.
2. Description of the Related Art
In the impression development art a development method is known which uses a single component system developer, and is characterized in that an electrostatic latent image and a developer particle or a developer carrier are brought into contact with each other at a relative peripheral speed of substantially zero, which is disclosed in U.S. Pat. Nos. 3,152,012 and 3,731,148, Published Unexamined Japanese Patent Applications No. 47-13088 and 47-13089, etc., and has the advantages that the developing apparatus can be simplified and reduced in size, and the developer can be easily colored, since no magnetic material is used.
In impression development, an elastic and conductive development roller is required for performing development with the developer carrier impressed on or in contact with the electrostatic latent image. If an electrostatic latent image holding member is rigid, it is essential that the development roller be formed of an elastic member to prevent the rigid holding member from being damaged. As is well-known, it is desirable that a conductive layer be formed on or near the surface of the developing roller and a bias voltage be applied thereto in order to obtain a development electrode effect and a bias effect in the developing roller. Since electric charges are applied to the developer by triboelectric charging between the developing roller and a developer layer forming blade, the blade has to be pressed against the developing roller to ensure a fixed nip width.
To ensure that sufficient charges are applied, to the developer, it is desirable that a triboelectric charging series material be used in accordance with the polarity of the charges. In reversal development as used in a laser printer, a digital PPC, and the like, wherein a photosensitive drum is negatively charged and development is performed using developer charged to the same polarity as that of the photosensitive drum, negative charges are applied to the developer, and thus silicone rubber is frequently used, since it is easy to charge positively. However, when silicone rubber is used, the end portion of the blade quickly becomes worn due to the short lifetime of the silicone rubber, which may cause a problem.